When blood flows into the subarachnoid space after rupture of an intracranial vessel, it is called subarachnoid hemorrhage. Spontaneous subarachnoid hemorrhage can be caused by a variety of etiologies. Clinical manifestations include acute onset of severe headache, vomiting, impaired consciousness, signs of meningeal irritation, and bloody cerebrospinal fluid.3 It accounts for 10%-15% of strokes. More than half of them are due to rupture of congenital intracranial aneurysms. The remainder are caused by a variety of other etiologies. There are many causes of subarachnoid hemorrhage, and the more common ones are listed below: ① Rupture of intracranial aneurysms and arteriovenous malformations, which together account for about 57% of all cases. ② Arterial rupture caused by hypertension and atherosclerosis ③ Hematological diseases, such as leukemia, hemophilia, pernicious anemia, etc. ④ Intracranial tumors, such as glioma and meningioma in the primary cases. metastases, such as bronchogenic lung cancer ⑤ Vascular allergic reactions, such as polyarteritis nodosa systemic lupus erythematosus, etc. ⑥ Brain and meningeal inflammation, including septic, bacterial, viral, tuberculosis, etc. (7) Complications of anticoagulation therapy. ⑧ Cerebrovascular occlusive disease causing hemorrhagic cerebral infarction. Anomalous vascular network disease of the cerebral base (moyamoya) often has subarachnoid hemorrhage as the main manifestation. ⑨ Thrombosis of intracranial veins. ⑩ Complications of pregnancy Clinical manifestations of subarachnoid hemorrhage can develop at any age. The most common manifestations are symptoms of increased intracranial pressure, disturbance of consciousness, signs of meningeal irritation, symptoms of cranial nerve injury, impairment of limb movement, and epilepsy. (I) Pre-hemorrhagic symptoms and triggers Some patients may have pioneer symptoms such as headache, dizziness and cranial nerve palsy days or weeks before. Only 1/3 of the patients with hemorrhage develop in the active state, such as relieving urine and stool, bending over, lifting weights, coughing and getting angry. (B) Post-hemorrhagic symptoms Due to the sudden rupture of pathological blood vessels, the onset of the disease is mostly acute. When bleeding, the patient suddenly feels a severe splitting-like pain in the head, which is distributed in the forehead, back of the head or the whole head, and may extend to the neck, shoulder, back, waist and legs. It is accompanied by pale face, cold sweat, nausea and vomiting. More than half of the patients have varying degrees of consciousness. In mild cases, there is transient confusion, and in severe cases, the coma gradually deepens. Some patients are always conscious, but may show apathy, drowsiness, and photophobia, small, fear of loud noises, and refusal to move, while some have delirium, xylophobia, disorientation and memory impairment, hallucinations and other psychiatric symptoms. Some patients are accompanied by partial or generalized seizures. At the beginning of the illness, the patient’s blood pressure rises and gradually returns to its original level after 1-2 days, the pulse rate is significantly accelerated, sometimes with irregular rhythm, and there is no significant change in respiration. After 24 hours of onset, fever, pulse instability, blood pressure fluctuations, excessive sweating, skin and mucous membrane congestion, and abdominal distension may gradually appear. Patients with severe hemorrhage may immediately fall into a deep coma, accompanied by deafferentation tonic seizures and brain herniation formation, which can quickly lead to death. The clinical manifestations of elderly patients are often atypical, with headaches being mostly inconspicuous, while psychiatric symptoms and disorders of consciousness are more common. (C) Physical signs Cervical tonicity, positive Kernig’s sign and Brusinsky’s sign. They often appear within 1-2 days of onset. These two are the most common signs of subarachnoid hemorrhage.